Question

ゲスト上ちゃん

for their only company ってどういうことですか？
あと、下線部（3）の訳を教えていただきたいのですが

Many working mothers have had to give up their jobs
The
(2) -
they cannot secure places for their children at such facilities.
problem has become severe, and even students who are fortunate
enough to receive admission to an after-school club benefit for only a
limited time. Many others stay home alone, often (3)with a TV or 15
computer for their only company.
nim at the problem and is trying to

(3) with a TV or computer for their only company
7. sitting on their own in front of a TV or computer
. playing with their friends rather than studying
. watching TV or playing computer games with their
mothers
I. using a TV or computer to collect information about a
job
1 their waiting lists.